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Definition

Fatigue is a common symptom. Almost everyone feels it during short-term illness. Fortunately, fatigue usually goes away when the illness is over.

But sometimes fatigue doesn't go away. It doesn't get better with rest. And the cause might be unclear.

Fatigue reduces energy, the ability to do things and the ability to focus. Ongoing fatigue affects quality of life and state of mind.

Causes

Most of the time fatigue can be traced to one or more lifestyle issues, such as poor sleep habits or lack of exercise. Fatigue can be caused by a medicine or linked to depression. Sometimes fatigue is a symptom of an illness that needs treatment.

Lifestyle factors

Fatigue may be related to:

• Alcohol or drug use
• Eating poorly
• Medicines, such as ones used to treat allergies or coughs
• Not enough sleep
• Too little physical activity
• Too much physical activity

Conditions

Exhaustion that doesn't let up might be a sign of:

• Adrenal insufficiency
• Amyotrophic lateral sclerosis (ALS)
• Anemia
• Anxiety disorders
• Cancer
• Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS)
• Chronic infection or inflammation
• Chronic kidney disease
• COPD
• Coronavirus disease 2019 (COVID-19)
• Depression (major depressive disorder)
• Diabetes
• Fibromyalgia
• Grief
• Heart disease
• Heart failure
• Hepatitis A
• Hepatitis B
• Hepatitis C
• HIV/AIDS
• Hyperthyroidism (overactive thyroid) also known as overactive thyroid.
• Hypothyroidism (underactive thyroid)
• Inflammatory bowel disease (IBD)
• Liver disease
• Low vitamin D
• Lupus
• Medicines and treatments, such as chemotherapy, radiation therapy, pain medicines, heart medicines and antidepressants
• Mononucleosis
• Multiple sclerosis
• Obesity
• Parkinson's disease
• Physical or emotional abuse
• Polymyalgia rheumatica
• Pregnancy
• Rheumatoid arthritis
• Sleep apnea — a condition in which breathing stops and starts many times during sleep.
• Stress
• Traumatic brain injury

When to see a doctor

Call 911 or your local emergency number

Get emergency help if you have fatigue and any of the following:

• Chest pain.
• Shortness of breath.
• Irregular or fast heartbeat.
• Feeling that you might pass out.
• Severe stomach, pelvic or back pain.
• Unusual bleeding, including bleeding from the rectum or vomiting blood.
• Severe headache.

Seek help for urgent mental health problems

Get emergency help if your fatigue is related to a mental health problem and your symptoms also include thoughts of harming yourself or of suicide. Call 911 or your local emergency services number right away. Or contact a suicide hotline. In the U.S., call or text 988 to reach the 988 Suicide & Crisis Lifeline. Or use the Lifeline Chat.

Schedule a doctor's visit

Call for an appointment with a health care provider if resting, reducing stress, eating well and drinking plenty of fluids for two or more weeks hasn't helped your fatigue.